docs: def get_selective_mirrors(self, number=None, pop_sorted=None):
          """get mirror genotypic directions of the `number` worst
          solution, based on ``pop_sorted`` attribute (from last
          iteration).
  
          Details:
          Takes the last ``number=sp.lam_mirr`` entries in
          ``pop_sorted=self.pop_sorted`` as solutions to be mirrored.
  
          """
          if pop_sorted is None:
              if hasattr(self, 'pop_sorted'):
                  pop_sorted = self.pop_sorted
              else:
                  return None
          if number is None:
              number = self.sp.lam_mirr
          res = []
          for i in xrange(1, number + 1):
              res.append(self.mean_old - pop_sorted[-i])
          return res